Light emitting device including base and base cap

ABSTRACT

A light emitting device includes: a base comprising a first wiring, a second wiring, and a third wiring; a first semiconductor laser element electrically connected to the first wiring and the second wiring, at an upper surface side of the base; a second semiconductor laser element electrically connected to the second wiring and the third wiring, at the upper surface side of the base; and a base cap fixed to the base such that the first semiconductor laser element and the second semiconductor laser element are enclosed in a space defined by the base and the base cap. The first semiconductor laser element and the second semiconductor laser element are connected in series. A portion of each of the first, second, and third wirings is exposed at the upper surface of the base at locations outside of the space defined by the base and the base cap.

CROSS-REFERENCE TO RELATED PATENT APPLICATIONS

The present application is a divisional of U.S. patent application Ser.No. 16/116,856, filed on Aug. 29, 2018, which claims priority under 35U. S. C. § 119 to Japanese Patent Application No. 2017-167144, filed onAug. 31, 2017 and Japanese Patent Application No. 2018-156001, filed onAug. 23, 2018, the contents of which are incorporated herein byreference in their entireties.

BACKGROUND

The present disclosure relates to a method of manufacturing a lightemitting device and a light emitting device.

There has been known a light emitting device having a plurality ofsemiconductor laser elements mounted and connected in series (forexample, see FIG. 4 of Japanese Publication No. 2016-518726 (withcorresponding PCT Publication No. WO 2014/183981).

SUMMARY

When inspecting driving of the semiconductor laser elements included insuch light emitting devices, each of the semiconductor laser elementsmay be inspected before being mounted, or a plurality of semiconductorlaser elements that have been mounted and connected in series may becollectively inspected. However, results reflecting the mounted state ofeach semiconductor laser element cannot be obtained in the former case,whereas accurate detecting of minute degradation of each of thesemiconductor laser elements is difficult in the latter case.

According to one embodiment of the present disclosure, a method ofmanufacturing a light emitting device includes, in this order: providinga light emitting device including, a base having a first wiring, asecond wiring and a third wiring, and a first semiconductor laserelement electrically connected to the first wiring and the secondwiring, at an upper surface side of the base, in which the firstsemiconductor laser element and the second semiconductor laser elementare connected in series; performing a first measurement by supplyingelectric current to the first semiconductor laser element through thefirst wiring and the second wiring to measure at least one property ofthe first semiconductor laser element, the at least one property of thefirst semiconductor element including at least an electrical property oran optical property, and supplying electric current to the secondsemiconductor laser element through the second wiring and the thirdwiring to measure at least one property of the second semiconductorlaser element, the at least one property of the second semiconductorlaser element including at least one of an electrical property or anoptical property; supplying electric current to the first semiconductorlaser element and the second semiconductor laser element for a length oftime; performing a second measurement by supplying electric current tothe first semiconductor laser element through the first wiring and thesecond wiring to measure the at least one property of the firstsemiconductor laser element, and supplying electric current to thesecond semiconductor laser element through the second wiring and thethird wiring to measure the at least one property of the secondsemiconductor laser element; and evaluating the first semiconductorlaser element based on the at least one property of the firstsemiconductor laser element measured during the first measurement andthe second measurement, and evaluating the second semiconductor laserelement based on the at least one property of the second semiconductorlaser element measured during the first measurement and the secondmeasurement.

A light emitting device according to one embodiment of the presentdisclosure includes: a base having a first wiring, a second wiring, anda third wiring; a first semiconductor laser element disposed at an uppersurface side of the base and electrically connected to the first wiringand the second wiring; a second semiconductor laser element disposed atthe upper surface side of the base and electrically connected to thesecond wiring and the third wiring; and a base cap being fixed to thebase such that the first semiconductor laser element and the secondsemiconductor laser element are enclosed in a space defined by the baseand the base cap. The first semiconductor laser element and the secondsemiconductor laser element are connected in series, and a portion ofthe first wiring, a portion of the second wiring, and a portion of thethird wiring are respectively exposed at the upper surface of the baseoutside of the space defined by the base and the base cap.

The method of manufacturing as described above allows for individualinspection of each of the semiconductor laser element, and thus canrealize a light emitting device of high reliability. The light emittingdevice described above can provide high reliability.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic perspective view of a light emitting deviceaccording to a first embodiment of the present invention.

FIG. 2 is a schematic cross-sectional view taken along line II-II ofFIG. 1.

FIG. 3 is a schematic perspective view illustrating the light emittingdevice according to the first embodiment.

FIG. 4 is an enlarged view of the portion enclosed by the dotted line inFIG. 3.

FIG. 5 is a top view illustrating a light emitting device according tothe first embodiment.

FIG. 6 is an enlarged view of the portion enclosed by the dotted line inFIG. 5.

FIG. 7 is a schematic perspective view illustrating a light emittingdevice according to the first embodiment.

FIG. 8 is a flowchart illustrating a method of manufacturing a lightemitting device according to the first embodiment.

DETAILED DESCRIPTION

Certain embodiments of the present invention will be described belowwith reference to the accompanying drawings. The embodiments shown beloware intended as illustrative to give a concrete form to technical ideasof the present invention, and the scope of the invention is not limitedto those described below. The sizes and the positional relationships ofthe members in each of the drawings are occasionally shown exaggeratedfor ease of explanation.

FIG. 1 is a schematic perspective view of a light emitting device 200Caccording to a first embodiment of the present invention, and FIG. 2 isa schematic cross-sectional view taken along line II-II of FIG. 1. FIG.3 is a schematic perspective view illustrating a light emitting device200A (i.e., a light source 200A), which shows a state of the lightemitting device 200C in which the base cap 30 and the cover 100 havebeen removed. FIG. 4 is an enlarged view of the portion enclosed by thedotted line in FIG. 3. FIG. 5 is a top view of the light emitting device200A, and FIG. 6 is an enlarged view of the portion enclosed by thedotted line in FIG. 5. FIG. 7 is a schematic perspective viewillustrating a light emitting device 200B (i.e., a light source withbase cap 200B), which shows a state in which the base cap 30 is fixed tothe light emitting device 200A. In the present specification, for thesimplicity of explanation, the term “light emitting device” refers to alight emitting device in which one or more semiconductor laser elements20 (hereinafter may be referred to as “LD element(s)”) are fixed on thebase 10. That is, the light source 200A in which one or more LD elements20 are fixed, the light source with base cap 200B in which the base cap30 is fixed to the light source 200A, and the light emitting device 200Cin which the cover 100 is fixed to the light source with base cap 200B,respectively, can serve as a “light emitting device”, and therefore, maybe collectively referred to as the “light emitting device 200”.

A method of manufacturing a light emitting device 200 according to thefirst embodiment includes, in this order: providing a light emittingdevice including: a base 10 having a first wiring 11 a, a second wiring11 b, and a third wiring 11 c; a first LD element 20 a being disposed atan upper surface side of the base 10 and electrically connected to thefirst wiring 11 a and to the second wiring 11 b, and a second LD element20 b being disposed at the upper surface side of the base 10 andelectrically connected to the second wiring 11 b and to the third wiring11 c; in which the first LD element 20 a and the second LD element 20 bare connected in series; performing a first measurement, includingsupplying electric current to the first LD element 20 a through thefirst wiring 11 a and the second wiring 11 b and measuring at least oneof an electric property or an optical property (hereinafter may bereferred to as “first property”) of the first LD element 20 a, andsupplying electric current to the second LD element 20 b through thesecond wiring 11 b and the third wiring 11 c and measuring the firstproperty of the second LD element 20 a; supplying electric current tothe first LD element 20 a and the second LD element 20 b for a certainlength of time or longer; performing a second measurement, includingsupplying electric current to the first LD element 20 a through thefirst wiring 11 a and the second wiring 11 b and measuring the firstproperty of the first LD element 20 a, and supplying electric current tothe second LD element 20 b through the second wiring 11 b and the thirdwiring 11 c and measuring the first property of the second LD element 20b; and respectively evaluating the first LD element 20 a and the secondLD element 20 b based on the first property of the first LD element 20 afrom the first measurement and the first property of the first LDelement 20 a from the second measurement, and on the first property ofthe second LD element 20 b from the first measurement and the firstproperty of the second LD element 20 b from the second measurement.

The method of manufacturing described above allows for individualinspection of properties of the first LD element 20 a and the second LDelement 20 b each in an operating state as a light emitting device(i.e., in a state in which each LD element 20 is mounted on the base10), which allows obtaining of a light emitting device of highreliability. More details thereof will be described below.

Because the same electric current can be supplied to each of thecomponents connected in series, in a light emitting device having two ormore LD elements, the two or more LD elements may be connected inseries. Inspection of properties of each LD element in such a lightemitting device may be carried out on individual LD elements beforemounting the LD elements, or collectively on the entire two or more LDelements, after mounting each of the two or more LD elements andconnecting them in series. However, the former way of inspection is notcapable of detecting degradation of the properties of the LD elementsdue to improper mounting or the like. In the latter way of inspection,although apparent degradation of the properties can be detected, minutedegradation of each of the LD elements cannot be detected. The latterway of inspection will be more specifically described below. Forinspecting presence or absence of improper application or the like ofthe bonding material located between each LD element and the base, aninspection for aging effects can be effective, in which a current higherthan the LD element was designed to use is kept applied for a relativelylong length of time and a change before and after applying the currentis inspected. However, in the case in which two LD elements areconnected in series, when one of the two LD elements has insufficientheat dissipation and exhibits a lower forward voltage (hereinafter maybe referred to as “Vf”) after the aging when compared to the Vf beforethe aging, and the other one of the two LD element has sufficient heatdissipation and exhibits a higher Vf after the aging when compared tothe Vf before the aging, such an individual deficiency may not bedetected when the LD elements connected in series are collectivelyinspected.

Accordingly, in the present embodiment, in the light emitting device 200that includes two or more LD elements 20 connected in series, the firstproperty of each of the LD elements, for example, the first LD element20 a and the second LD element 20 b, are individually inspected usingthe first wiring 11 a, the second wiring 11 b, and the third wiring 11c. Thus, individual inspection on each of the LD elements 20 can realizechecking of properties of each of the LD elements, which allows forobtaining light emitting devices with high reliability. For example,light emitting devices in vehicular lighting are required to exhibitlittle change in the properties for a long length of time. Accordingly,the light emitting devices according to the present embodiment areparticularly suitable to the use in vehicular lighting etc.

In the below, a method of manufacturing a light emitting device 200 willbe described with reference to the process flow chart shown in FIG. 8.

Providing Light Emitting Device

The light emitting device 200 is provided. In the present embodiment,first, the light emitting device 200A shown in FIG. 3 to FIG .6 isprovided. The first light emitting device 200A includes a base 10 havinga first wiring 11 a, a second wiring 11 b, and a third wiring 11 c, afirst LD element 20 a disposed on an upper surface of the first wiring11 a and being electrically connected to the first wiring 11 a and thesecond wiring 11 b, and a second LD element 20 b disposed on an uppersurface of the second wiring 11 b and being electrically connected tothe second wiring 11 b and the third wiring 11 c. The first LD element20 a and the second LD element 20 b are connected in series.

The base 10 includes at least three wirings 11 a to 11 c. In the firstembodiment, seven wirings 11 a to 11 g are included. The base 10 has alayered structure containing a plurality of insulating layers. The firstwiring 11 a serves as a part of the upper surface of the base 10 locatedinward of the first frame 12 and a part of the upper surface of the base10 located outward of the first frame 12. The portion of the firstwiring 11 a located inward of the first frame 12 and the part of thefirst wiring 11 a located outward of the first frame 12 are electricallyconnected by a part of the first wiring 11 a located inside the base 10.Examples of the materials for the insulating layers include AlN, Si₃N4,SiC, ZrO₂, Al₂O₃, and sapphire, and examples of the materials for thewiring 11 include Cu and Au. Other components of the wiring 11, thesecond wiring 11 b and successive wirings, can also have configurationssimilar to that of the first wiring 11 a.

The first wiring 11 a is used for the measurement of the properties ofthe first LD element 20 a and for driving a plurality of LD elements 20that are connected in series. That is, the first wiring 11 a is a commonwiring that is used at the time of individually driving the first LDelement 20 a for the measurement and also at the time of driving thefirst LD element 20 a together with other LD elements 20. With thisconfiguration, the number of wirings can be reduced, which allows foremploying a base of simpler structure. In the present embodiment, theseventh wiring 11 g is also used as a common wiring line. In the presentembodiment, the first wiring 11 a includes two wiring parts inward ofthe first frame 12. The first sub-mount 50 a mounted with the first LDelement 20 a is disposed on one of the two first wiring parts, and theother of the two first wiring parts is directly connected to the firstwiring part 11 a located outward of the first frame 12. The other of thetwo first wiring parts and the first sub-mount 50 a are connected by thefirst wires 81. The first wiring 11 a may be formed with a single wiringpart as in the second wiring 11 b. The fourth wiring 11 d includes threewiring parts inward of the first frame 12, but the fourth wiring 11 dmay be formed with a single wiring part as in the first wiring 11 a.

The base 10 includes the first frame 12 surrounding two or more LDelements 20. The first frame 12 can be connected by way of welding, forexample. When welding is used, the first frame 12 is preferably made ofa material that contains Fe as its main component. Other examples of thematerials of the first frame 12 include a single body of Cu, Al, Fe, Au,or Ag, and an alloy of those.

The base 10 further includes a second frame 13 surrounding the firstframe 12. The second frame 13 can be connected by using a brazingmaterial, for example. Examples of the materials of the second frame 13include a single body of Cu, Al, Fe, Au, or Ag, and an alloy of those.

On the upper surface of the base 10 inward of the first frame 12, two ormore sub-mounts 50 are arranged and a single LD element 20 is mounted oneach of the sub-mounts 50. More specifically, the first LD element 20 ais disposed on the upper surface of the first wiring 11 a via the firstsub-mount 50 a, and the second LD element 20 b is disposed on the uppersurface of the second wiring 11 b via the second sub-mount 50 b. In asimilar manner, other LD elements 20 such as the third LD element aredisposed on the upper surfaces of the wirings 11 such as the thirdwiring 11 c via the sub-mounts 50 such as the third sub-mount 50 c,respectively. In the present embodiment, each of the LD elements 20 isfixed on the corresponding sub-mount 50 via an electrically conductivelayer 60 made of, for example, Au—Sn. The LD elements 20 are connectedin series by the first wires (thin metal wires) 81.

The LD elements 20 are configured to emit laser light as excitationlight to excite a fluorescent material contained in the fluorescent part111. The light emitted from the LD elements 20 preferably have a peakwavelength in a range of 320 nm to 530 nm, more preferably in a range of430 nm to 480 nm. For such LD elements 20, LD elements that include anitride semiconductor can be employed. It is preferable to use the LDelements 20 whose first property have already been inspected beforemounting on the base 10. With this arrangement, deficiency caused by theproperties of the LD elements 20 can be reduced.

In the present embodiment, all the LD elements 20 arranged inward of thefirst frame 12 are connected in series. Accordingly, a certain amount ofcurrent can be supplied equally to each of the LD elements 20, and thus,variation in the emission intensity among the LD elements 20 can bereduced. The LD elements 20 may be connected such that some of the LDelements 20 are connected in series and the rest of the LD elements 20are connected in series, thus two or more groups of the LD elements eachconnected in series may be provided.

The sub-mounts 50 preferably have a thermal expansion coefficientbetween the thermal expansion coefficient of the base 10 and the thermalexpansion coefficient of the LD elements 20. Accordingly, detachment ofthe LD elements 20 and/or detachment of the sub-mounts 50 can bereduced. When a material containing a nitride semiconductor is used forthe LD elements 20, aluminum nitride or silicon carbide can be used forthe sub-mounts 50. In the present embodiment, the second and subsequentsub-mounts 50 b to 50 f each has a configuration similar to that of thefirst sub-mount 50 a, but all the sub-mounts may have differentconfigurations.

Each of the sub-mounts 50 is fixed to the base 10 by using the methoddescribed below. The first laser device having the first LD element 20 amounted on the first sub-mount 50 a and the second laser device havingthe second LD element 20 b mounted on the second sub-mount 50 b arerespectively mounted on the upper surface of the base 10 via a bondingmaterial containing nano-metal particles or sub-micron metal particlesand an organic solvent. The first laser device is mounted on the firstwiring 11 a and the second laser device is mounted on the second wiring11 b. Subsequently, the bonding material is heated to bond the firstlaser device and the second laser device to the base 10 at once. At thistime, application of uniform pressure to all the laser devices isdifficult due to variation of heights of the laser devices. Thus, thefirst laser device and the second laser devices are bonded to the base10 without pressing the devices onto the base 10. With the use of thismethod, a plurality of laser devices can be fixed to the base 10 at oncewithout applying an excessive heat on the bonding material. Thus, thismethod is suitable for fixing a plurality of laser devices, but maycreate uneven mounting states. For example, if a gap is created betweenthe laser device and the base, heat generated from the LD elements 20may be difficult to disperse, which may accelerate degradation of the LDelements 20. The method of manufacturing according to the presentembodiment allows inspection of the laser devices in their mountedstate, which allows evaluation of properties of each of the LD elements20 taking into consideration the mounting state of the laser device.

The first sub-mount 50 a and the base 10, and the second sub-mount 50 band the base 10 are respectively bonded by nano-metal particles orsub-micron metal particles. In the present embodiment, sub-micron goldparticles are used. In the present disclosure, the term “nano-metalparticles” refers to metal particles having an average particle size ina range of 1 nm to 100 nm, and the term “sub-micron metal particles”refers to metal particles having an average particle size in a range of101 nm to 1 μm. Average particle size can be determined, for example, byusing a projected image produced by a transmission electron microscope(TEM), randomly measuring projected area circle equivalent diameters of100 nano-metal particles or metal sub-micron particles, and calculatingthe average value.

In order to prevent damage on the LD elements 20, a protective element70 such as Zener diode may be provided on each sub-mount 50. Each of theprotective elements 70 is electrically connected to the LD elements 20via a wire.

The second wiring 11 b and the second sub-mount 50 b are connected bythe second wires 82 (hereinafter, a wire (or wires) used in seriesconnection may be referred to as a “first wire 81 (or first wires 81)”and other wires may be referred to as “second wire(s) 82”). Thus, it ispossible to individually drive the first semiconductor laser element 20a and the second semiconductor laser element 20 b, for example, forindividually measuring the first property of the first semiconductorlaser element 20 a and the second semiconductor laser element 20 b.

The second sub-mount 50 b and the second wiring 11 b are connected by aplurality of second wires 82. The number of the first wires 81 ispreferably greater than the number of the second wires 82. The lengthsof the second wires 82 are preferably shorter than the lengths of thefirst wires 81. For example, the length of one of the second wires 82 ispreferably shorter than the length of one of the first wires 81. This isbecause the second wires 82 are highly unlikely to be employed in theactual driving of the light emitting device and therefore it is enoughfor the second wires 82 to have numbers and lengths that are sufficientto supply electric current for performing the first measurement and thesecond measurement. The same can be applied to the second wires 82 thatconnect third and subsequent sub-mounts 50 and the third and subsequentwirings 11 c to 11 g respectively.

The light-reflecting parts 40 are disposed on an upper surface side ofthe base 10 via the wirings. The light-reflecting parts 40 areconfigured to reflect the light from their corresponding LD elements 20upward. For example, a mirror having at least a portion of its surfaceformed with a reflecting film such as a dielectric multilayer film canbe used as the light-reflecting parts 40. As shown in FIG. 3 and FIG. 4,a single light-reflecting part 40 can be provided for a single LDelement 20.

In the present embodiment, the first measurement is performed in a stateof the light emitting device 200B shown in FIG. 7. In the light emittingdevice 200B, the base cap 30 is fixed to the base 10 to make the space(hereinafter referred to as “space S”) confining the first LD element 20a and the second LD element 20 b hermetically sealed. The firstmeasurement may be performed on the light emitting device 200A in whichthe base cap 30 has not been provided. In the light emitting device200B, a portion of the first wiring 11 a, a portion of the second wiring11 b, and a portion of the third wiring 11 c are exposed on the uppersurface of the base 10 at locations outside of the space S. The LDelements 20 that include a nitride semiconductor have a high energydensity in the light emission surfaces, which tend to attract dust suchas an organic material to their light emission end surfaces. Withhermetically sealing the space S, attracting of dust to the lightemission surfaces of the LD elements 20 can be reduced.

The base cap 30 includes a support 31, a first light-transmissive part33 held by a lower surface of the support 31, and an adhesive member 32bonding the support 31 and the first light-transmissive part 33. Thesupport 31 is connected to the first frame 12 by welding or the like.The support 31 defines a through-opening to allow light from the LDs topass through. The first light-transmissive part 33 is fixed to cover thethrough-opening of the support 31. The support 31 is preferably made ofa material that contains Fe as its main component. Other examples of thematerials of the support 31 include a single body of Cu, Al, Fe, Au, orAg, and an alloy of those. The first light-transmissive part 33 can beformed with glass, sapphire, or the like. The first light-transmissivepart 33 can have a thickness in a range of, for example, 0.1 mm to 2 mm.

In the present embodiment, the space S is defined by the base 10, thefirst frame 12, and the base cap 30. Alternatively, the space S may bedefined by a plate-shaped base and a cover 30 that is formed with adownward opening recess. In other words, the base cap 30 may be disposedon the upper surface of the base such that a plurality of LD elementscan be disposed in the recess.

Performing a First Measurement

Next, the first property of the first LD element 20 a is measured bysupplying electric current to the first LD element 20 a through thefirst wiring 10 a and the second wiring 11 b, and the first property ofthe second LD element 20 b is measured by supplying electric current tothe second LD element 20 b through the second wiring 11 b and the thirdwiring 11 c. Hereinafter, the performance of the first measurement mayalso be referred to as “the first measuring step,” and the performanceof the second measurement may also be referred to as “the secondmeasuring step.” In the first measuring step, the same first property ismeasured on the first LD element 20 a and the second LD element 20 b. Inthe first measuring step, electric current is supplied for a relativelyshort time at a value higher than its designated value for use indriving the light emitting device. The third and subsequent LD elements20 c to 20 f are also supplied with the electric current in the samemanner to measure the first property.

The method of measuring the first property of each of the LD elements 20will be described below with reference to FIG. 5. The first property ofthe first LD element 20 a is measured with supplying electric current tothe first wiring 11 a located outside of the first frame 12 and to thesecond wiring 11 b located outside of the first frame 12. The electriccurrent from the first wiring 11 a flows through the wiring part, thefirst wire 81, the electrically conductive layer 60 on the firstsub-mount 50 a, the first LD element 20 a, the first wire 81, theelectrically conductive layer 60 on the second sub-mount 50 b, thesecond wire 82, and the second wiring 11 b, in this order. With thisarrangement, only the first LD element 20 a emits light. In this firstmeasuring step, for example, the value of the electric current isgradually increased from 0 A to 4 A in four seconds, while continuouslymeasuring the first property. Next, the first property of the second LDelement 20 b is measured. The measuring of the first property of thesecond LD element 20 b is carried out in the same manner with supplyingelectric current to the second wiring 11 b and the third wiring 11 c.The measuring of the first property of each of the third and subsequentLD elements 20 is also carried out in the same manner.

In the present disclosure, the term “electrical property” refers, forexample, to Vf and the term “optical property” refers, for example, toat least one of far field pattern (FFP), wavelength, and light output.In the first measuring step, at least Vf is preferably measured, and atleast Vf and FFP are more preferably measured. When all of the pluralityof LD elements that are connected in series are turned ON to emit lightand are collectively measured, properties of individual LD elements 20cannot be determined, but as in the present embodiment, individuallymeasuring each one of the plurality of LD elements 20 allows fordetermining properties of each LED element, and thus evaluation of eachof the plurality of LD elements can be facilitated.

In the first measuring step, in view of attracting dust to the LDelements 20, each measurement is preferably carried out in the state ofthe light emitting device 200B. When the measuring at the first time iscarried out in the state of the light emitting device 200A, the cap isfixed to the base to obtain the state of the light emitting device 200Bbetween the first measuring step and a step of supplying electricalcurrent for a certain length of time or longer.

Supplying Electric Current for Certain Length of Time or Longer

Next, electric current is supplied to each LD element 20 for a certainlength of time or longer. In this step, electric current greater thanthreshold current is supplied to all the LD elements 20 mounted on thebase 10 for a certain length of time. As described above, with supplyinga relatively high electric current for a certain length of time orlonger, inspection of time-depending change of each of the LD elements20 can be facilitated to be done relatively shorter. The length of timeto supply electric current can be changed according to the value of theelectric current to be supplied. For example, a length in a range of 1hour to 20 hours is preferable, and a range of 5 hours to 15 hours ismore preferable. Supplying the electric current for equal to or longerthan the minimum length of time shown above allows for facilitatingdetection of initial defectiveness of the LD elements, and supplying theelectric current for equal to or shorter than the maximum length of timeshown above allows for reducing degradation of the LD elements. Forexample, in an ambient temperature surrounding the light emitting deviceof 20° C., a pulse current of 14 A is applied for about 9.5 hours.

In the present embodiment, the electric current is supplied to the firstLD element 20 a and the second LD element 20 b that are connected inseries. In other words, the electric current is supplied to all the LDelements 20 by using the first wires 81. With this arrangement, theelectric current can be supplied collectively to the plurality of LDelements 20, and thus time-depending changes of all the LD elements canbe determined in a short length of time. In the first measuring step,alternatively, the electric current can be supplied to each of the LDelements through the second wires 82 connected to the sub-mount 50 andthe wiring 11.

Performing a Second Measurement

Next, the first property of each of the LD elements 20 are measured in asimilar manner as in the first measuring step. Specifically, the firstproperty of the first LD element 20 a is measured by supplying electriccurrent to the first LD element 20 a through the first wiring 10 a andthe second wiring 11 b, and the first property of the second LD element20 b is measured by supplying electric current to the second LD element20 b through the second wiring 11 b and the third wiring 11 c.

Evaluating Semiconductor Laser Element

Next, each of the LD elements 20 are evaluated based on the firstproperty determined by the first measuring step and the first propertydetermined by the second measuring step. More specifically, each of theLD elements 20 are evaluated such that the first LD element 20 a isevaluated based on the first property of the first LD element 20 adetermined by the first measuring step and the first property of thefirst LD element 20 a determined by the second measuring step, and thesecond LD element 20 b is evaluated based on the first property of thesecond LD element 20 b determined by the first measuring step and thefirst property of the second LD element 20 b determined by the secondmeasuring step.

For example, presence of a defect in the bonding between the LD element20 and the wiring 11 results in a lower Vf value obtained by the secondmeasuring step than a Vf value obtained by the first measuring step.This is thought to be due to high temperature of the LD elements 20caused by a defect in the bonding that impedes dissipation of heatgenerated by the LD elements to the base 10, which increases thetemperature of the LD elements. If the LD elements are driven in thisstate, the amount of the electric current increases and that furtherincreases the amount of heat generated from the LD elements 20, whichincreases degradation of the LD elements 20. For this reason, anexcessive decrease in the Vf value obtained by the second measuring stepis determined to be defective. For example, the Vf value of 3.6 or less,or 4.1 or greater is determined to be defective. When a nitridesemiconductor is used in the LD element 20 and the space S is notsufficiently hermetically sealed, dust may be attracted to the LDelements 20 in the step of supplying electric current for a certainlength of time or longer, which may result in difference in the FFPobtained by the first measuring step and the FFP obtained by the secondmeasuring step. For example, the peak of the FFP obtained by the secondmeasuring step shifts from the peak of the FFP obtained by the firstmeasuring step. When the optical output is measured, for example, anoptical output of 2.2 W or less, or 2.75 W or greater is determined tobe defective. Further, when the wavelength is measured, and a desiredpeak wavelength of the LD elements 20 is 450 nm, a wavelength of 445 nmor shorter, or 455 nm or longer is determined to be defective. Thosevalues are determined to be defective because driving the light emittingdevice with such a condition may change the optical properties. In thepresent embodiment, the first property is measured in the firstmeasuring step and the second measuring step. However, when a referencevalue of the first property used to compare with the value of the firstproperty measured in the second measuring step to determine whether thesemiconductor laser element 20 is defective is preliminarily provided,the first measuring step may be omitted. That is, the reference value ofthe first property is compared with the value of the first propertymeasured in the second measuring step to determine whether thesemiconductor laser element 20 is defective. Further, when a referencevalue of the first property used to compare with the value of the firstproperty measured in the first measuring step to determine whether thesemiconductor laser element 20 is defective is preliminarily provided,the step of supplying electric current for a certain length of time orlonger and the second measuring step may be omitted. That is, when thevalues of the first property measured in the first measuring step can beevaluated without inspection of time-depending change, the step ofsupplying electric current for a certain length of time or longer andthe second measuring step may be omitted. In this case, the referencevalue of the first property is compared with the value of the firstproperty measured in the first measuring step to determine whether thesemiconductor laser element 20 is defective.

In this case, deviation in the properties obtained by the measuring isclassified into a plurality of ranks. Accordingly, uniformity ofproperties of the LD elements 20 can be enhanced. For example, the VFvalues of the LD elements 20 are classified in ranks. The light emittingdevice(s) having the LD element(s) 20 that does not meet a predeterminedrange of ranks is determined to be defective. However, the quality maybe determined without creating ranks.

Fixing Second Light-Transmissive Part 90 and Cover 100

Next, a second light-transmissive part 90 is disposed on the uppersurface of the base cap 30 to cover the upper-end of the through-openingof the support 31. The second light-transmissive part 90 serves as alens configured to refract the laser light from each of the LD elements20 such that the laser light from each of the LD element is irradiatedon the lower surface of the fluorescent part 111. Examples of thematerial of the second light-transmissive part 90 include opticalglasses such as BK7, and light-transmissive resins. The secondlight-transmissive part 90 can have a thickness in a range of, forexample, 1 mm to 5 mm.

Subsequently, a cover 100 defining an opening is fixed on the uppersurface of the second frame 13. An optical component 110 is disposed tocover the opening of the cover 100. The second light-shielding part 120is disposed between the lateral surfaces of the optical component 110and the cover 100 to shield the light from the optical component 110.The cover 100 has a lateral part widening downward. This configurationincreases the volume that allows dissipation of heat, and accordingly,heat generated in the optical component 110 can be dissipatedefficiently.

The optical component 110 includes a fluorescent part 111, a firstlight-shielding part 112 disposed on the lateral surfaces of thefluorescent part 111, a dielectric multilayer film 113 disposed on thelower surface of the fluorescent part 111, a thermally-conducting member114 disposed on the lower surface of the dielectric multilayer film 113,and an anti-reflecting filter 115 disposed on the lower surface of thethermally-conducting member 114. Disposing the thermally-conductingmember 114 at location directly under the fluorescent part 111 via thedielectric multilayer film 113 that is configured to reflect fluorescentlight can facilitate extraction of the fluorescent light whiledissipating the heat generated by the fluorescent part 111. Thefluorescent part 111 contains one or more fluorescent materials. Forexample, at least one fluorescent material among YAG phosphors, LAGphosphors, and Ca-α sialon phosphors can be contained. For the firstlight-shielding part, light-shielding ceramics such as alumina can beused. For the thermally-conducting member 114, for example, sapphire,SiC, or the like can be used.

When seen from above, the second light-shielding part 120 is arrangedsurrounding the optical component 110. As shown in FIG. 2, the secondlight-shielding part 120 is disposed to cover entire lateral surfaces ofthe heat conducting part 114. With this arrangement, lateraltransmission of light from the thermally-conducting member 114 can beprevented or reduced. For the second light-shielding part 120, forexample, a resin material added with light scattering particles such astitanium oxide can be used.

In the present embodiment, the optical properties are measured by thefirst measuring step and the second measuring step, and therefore, thesecond light-transmissive part 90 and the cover 100 are fixed to thebase cap 30 and the base 10 after the second measuring step. Thisfacilitates accurate evaluation of the first property of each of the LDelements 20. Moreover, the cover 100 and some other components are fixedafter evaluating the measuring results, which prevents components suchas the cover 100 to be wasted. When only the electrical properties aremeasured in the first measuring step and the second measuring step, thefixing of the second light-transmissive part 90 and the cover 100 to thebase cap 30 and the base 10 can be performed before performing the firstmeasuring step. In other words, providing the light emitting device 200Cin the step of providing a light emitting device and then the firstmeasuring step may be performed.

The second wires 82 may be disconnected by supplying electric currentthat is equal to or greater than a certain amount to the second wires 82after the second measuring step. When a connection is in series, anexternal terminal is connected to the first wiring 11 a, but if theexternal terminal is connected to both the first wiring 11 a and thesecond wiring 11 b due to a positional deviation of the externalterminal, uniform supply of the current to the first LD element 20 a andthe second LD element 20 b may be impeded, which may result in unevenemission from all the LD elements 20 that are connected in series.Whereas, disconnecting the second wires 82 can prevent flow of currentto the second LD elements 20 b when the external terminal isunintentionally connected to the second wiring 11 b, which canfacilitate supplying of electric current more uniformly. For example,when the second wires 82 are made of Au and have a diameter of 60 μm,the second wires 82 can be disconnected by supplying an electric currentof about 7.8 A to a single second wire 82.

The light emitting devices according to the embodiments can be used forvehicular lightings etc.

It is to be understood that, although the present invention has beendescribed with regard to preferred embodiments thereof, various otherembodiments and variants may occur to those skilled in the art, whichare within the scope and spirit of the invention, and such otherembodiments and variants are intended to be covered by the followingclaims.

What is claimed is:
 1. A light emitting device comprising: a basecomprising a first wiring, a second wiring, and a third wiring; a firstsemiconductor laser element electrically connected to the first wiringand the second wiring, at an upper surface side of the base; a secondsemiconductor laser element electrically connected to the second wiringand the third wiring, at the upper surface side of the base; and a basecap fixed to the base such that the first semiconductor laser elementand the second semiconductor laser element are enclosed in a spacedefined by the base and the base cap; wherein the first semiconductorlaser element and the second semiconductor laser element are connectedin series; and wherein a portion of the first wiring, a portion of thesecond wiring, and a portion of the third wiring are exposed at theupper surface of the base at locations outside of the space defined bythe base and the base cap.
 2. The light emitting device according toclaim 1, wherein: each of the first semiconductor laser element and thesecond semiconductor laser element comprises a nitride semiconductor,and the space defined by the base and the base cap is a hermeticallysealed space.
 3. The light emitting device according to claim 1, furthercomprising: a sub-mount disposed between the second semiconductor laserelement and the second wiring, wherein the second wiring and thesub-mount are connected by a wire.
 4. The light emitting deviceaccording to claim 3, wherein: the sub-mount and the second wiring areconnected by a plurality of wires.
 5. The light emitting deviceaccording to claim 1, wherein: the first semiconductor laser element isdisposed on the upper surface side of the base via a first sub-mount,the second semiconductor laser element is disposed on the upper surfaceside of the base via a second sub-mount, and the first sub-mount and thesecond sub-mount are bonded to the base by metal nanoparticles or metalsub-micron particles.
 6. The light emitting device according to claim 1,wherein: the first wiring comprises two wiring parts.
 7. The lightemitting device according to claim 1, wherein: the semiconductor laserelement is configured to emit light that has a peak wavelength in arange of 320 nm to 530 nm.
 8. The light emitting device according toclaim 1, further comprising: a light reflecting member configured toreflect light emitted from a corresponding semiconductor laser elementupward.
 9. The light emitting device according to claim 1, wherein: thebase cap comprises a support, a light-transmissive part held by a lowersurface of the support, and an adhesive member bonding the support andthe light-transmissive part.
 10. The light emitting device according toclaim 9, the light-transmissive part has a thickness in a range of 0.1mm to 2 mm.
 11. The light emitting device according to claim 9, wherein:the base comprises a frame surrounding the first semiconductor laser andthe second semiconductor laser in a top view, and wherein the support ofthe base cap is connected to the frame of the base.
 12. The lightemitting device according to claim 11, wherein: the first wiringcomprises: a first part that is located at an upper surface of the baseat a location inward of the frame, and a second part that is exposed ata location outward of the frame in the top view.
 13. The light emittingdevice according to claim 11, wherein: the frame is made of a materialthat contains Fe.